Heat Medium Circulation Control for Heat Exchanger Freeze Prevention
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Solution Overview
Problem
Existing heat medium cycle systems cannot continuously operate when water freezes in the heat exchanger, as they rely solely on water pressure sensors to prevent freezing, leading to system shutdowns and potential heat exchanger damage.
Innovation Solution
A heat medium cycle system that uses a controller to maintain a minimum flow rate, calculated based on inlet and outlet pressure sensors, to prevent freezing in the heat exchanger, allowing continuous operation and reducing the risk of heat exchanger damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the water flow rate is reduced to save power, then water sending power is reduced, but the water heat exchanger may freeze and break
Solution Approach 1:
The system performs preliminary action by calculating the minimum required flow rate before freezing occurs, using pressure difference measurements and pre-stored characteristics data. This allows the system to maintain safe operating conditions proactively rather than reacting after freezing begins, enabling power savings while preventing the harmful effect of heat exchanger freezing.
Solution Approach 2:
The system implements feedback by continuously measuring the pressure difference across the heat exchanger, comparing it against characteristic data, and adjusting the water flow rate accordingly. This closed-loop control ensures the flow rate remains above the minimum threshold needed to prevent freezing, allowing optimal power consumption while maintaining reliability.
2Reliability
If the system shuts down when water freezes to prevent damage, then heat exchanger damage is prevented, but the system cannot operate continuously
Solution Approach 1:
The system prevents freezing before it occurs by calculating minimum flow rates and adjusting water circulation in advance. This proactive approach eliminates the need for shutdowns, allowing continuous operation while maintaining heat exchanger protection. The characteristic data stored in advance enables quick adjustments without system interruption.
Solution Approach 2:
The system maintains continuous operation by using feedback control to adjust water flow rates dynamically. Instead of shutting down when freezing risks are detected, the system continuously monitors pressure differences and adjusts flow to maintain safe operating conditions, ensuring both continuous productivity and heat exchanger protection.
3Device complexity
If water pressure sensors are used only to inhibit compressor operation, then simple control is maintained, but the sensors are not effectively used for other purposes
Solution Approach 1:
The water pressure sensors serve multiple functions: they inhibit compressor operation when appropriate and simultaneously calculate water flow rates to prevent heat exchanger freezing. This multi-functionality increases sensor utilization without adding complexity, as the same sensors provide data for both control purposes.
Solution Approach 2:
The system merges the function of flow rate measurement and freezing prevention into the existing pressure sensor infrastructure. By combining the compressor control function with the new flow rate calculation function, the system achieves versatile sensor utilization while maintaining simple control architecture, avoiding the need for additional sensors or complex systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively prevents water from freezing in the heat exchanger, enabling continuous operation and reducing power consumption by maintaining a minimum flow rate, thus enhancing convenience and efficiency.
Implementation Method 1
measuring a pressure difference between an inlet and an outlet of the water heat exchanger by using a water pressure sensor provided at the water inlet and a water pressure sensor provided at the water outlet
Implementation Method 2
a water circulating pump circulating the water
Implementation Method 3
a water heat exchanger cooling the water to a target temperature by using heat from the refrigerant
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
Provided is a heat medium cycle system capable of being continuously operated while a heat medium is being prevented from freezing in a heat medium heat exchanger by using a pressure difference of the heat medium obtained from a measurement value of an inlet pressure sensor provided at an inlet of the heat medium heat exchanger and a measurement value of an outlet pressure sensor provided at an outlet of the heat medium heat exchanger. The heat medium cycle system includes a refrigeration cycle circuit, a heat medium cycle circuit, an inlet temperature sensor, the inlet pressure sensor, the outlet pressure sensor, an evaporating temperature sensor, and a controller. Under a first condition where the heat medium is to freeze in the heat medium heat exchanger, the controller is configured to obtain a minimum on-state flow rate at which the heat medium is kept from freezing in the heat medium heat exchanger, on the basis of a temperature of the heat medium at a heat medium inlet measured by the inlet temperature sensor and an evaporating temperature of refrigerant detected by the evaporating temperature sensor, and control a pump in such a manner that the minimum on-state flow rate is maintained to make the pressure difference of the heat medium obtained from a measurement value of the inlet pressure sensor and a measurement value of the outlet pressure sensor into a minimum on-state pressure difference.